为解决自动制造系统中的死锁问题,提出一种将混合整数规划算法和Petri网相结合的迭代式预防策略。在该策略中,混合整数规划算法中的0/1变量用来表示Petri网模型中的库所和变迁是否与一个最大的可被清空的信标相关。由于从一个最大的可被清空的信标中可以容易地计算出一个严格极小信标,就可以在不遍历所有的严格极小信标的情况下,直接求得一组基本信标,从而大大地降低了策略的时间算法复杂度。同时,控制该组基本信标可以确保目标系统具有简单的控制器结构和尽可能多的许可行为。实验结果表明了该控制策略的有效性和高效性。
To solve the deadlock problem arising in automated manufacturing systems,an iterative deadlock prevention policy via the combination of Mixed Integer Programming (MIP) and Petri nets was proposed. According to such a policy, any one of the 0/1 variables in an MIP model could be employed to detect whether or not a place or transition in the corresponding Petri net was related to a maximally emptied siphon, from which one strict minimal siphon could be easily extracted. Subsequently, this policy could derive a set of elementary siphons without enumeration of all the strict minimal siphons so that its time complexity was remarkably decreased. Furthermore, the control of such a set of elementary siphons would lead to a more permissive system with a much simpler supervisor. Experimental results validated the effectiveness and efficiency of the proposed policy.